(a) Field of the Invention
The present invention relates to a liquid crystal display (LCD). More specifically, the present invention relates to a pixel forming circuit for driving an LCD with low power.
(b) Description of the Related Art
An LCD generally comprises an LCD unit including an LCD panel having liquid crystal cells between two glass substrates in a matrix pattern, a backlight unit provided on the rear side of the LCD panel, a printed circuit board (PCB) unit for driving the LCD panel, and a case for protecting and integrating the units. Here, the PCB unit is a driving circuit for receiving red R, green G and blue B image data and synchronization signals, processing the same, and providing image data, scanning signals and timing control signals to the LCD panel so that the LCD panel normally displays computer images, television image and other images. The PCB unit comprises a plurality of PCBs and a plurality of flexible printed cables (FPC) for transmitting signals between the PCBs.
Referring to FIG. 1 showing a schematic diagram of a conventional LCD, a PCB unit of relative low resolution such as SVGA (600×800) for driving the LCD panel 40 on the rear side of the LCD panel 40 comprises a main PCB 10 for receiving the R, G and B image data and the synchronization signals, processing the same using a timing controller that is a customized integrated circuit (IC) of a flat pin grid array (FPGA) type, and processing and generating the image data and various control signals; a scan driver PCB 20 having a scan driver IC tape automated bond (TAB) that provides scanning signals to scan signal lines according to scan driver control signals provided by the main PCB 10; and a source driver PCB 30 having a source driver IC TAB that receives the image data and the control signals processed and provided by the main PCB 10, and provides the same to the LCD panel 40.
Referring to FIG. 2, a pixel configuration on the LCD panel comprises a scan signal line 21 for transmitting the scanning signals provided by the scan driver IC TAB of the scan driver PCB 20, a source signal line 31 for transmitting the image signals provided by the source driver IC TAB of the source driver PCB 30, liquid crystal 42, a metal oxide semiconductor (MOS) type thin film transistor (TFT) 41 for receiving the scanning signals and the image signals and transmitting the same to the liquid crystal 42 and a storage capacitor 43. At this time, the TFT 41 is turned off when receiving the scanning signal via a gate electrode, and receives the image signals from the source signal line 31 via a source electrode and transmits the same to the liquid crystal 42 and the storage capacitor 43 when the scanning signal is in high state. Next, when the scanning signal is in low state, the image signals stored in the liquid crystal 42 and the storage capacitor 43 are maintained during a frame set for respective resolutions.
However, the consuming power for driving the LCD adapted to notebook computers, portable personal digital assistants (PDA) and reflective PDAs ranges from several tens to several hundred watts [W] according to the size of the LCD panel. This power becomes a problem when a user goes out and uses the battery for a long time. Therefore, increased lifetime of the battery by low power consumption becomes main factor in business competitiveness.